Long Term Evolution (LTE) represents a significant change to the 3G UMTS/HSPA radio access and core networks. LTE uses a flat, IP-based network architecture. A common, packet-based infrastructure is used for all services (voice and data), removing the need for the dedicated circuit-switched and packet-switched domains which are present in 3G UMTS/HSPA network.
The radio access network is simplified in LTE with the base station, or evolved NodeB (eNodeB), implementing the functions which were previously distributed between the 3G RNC and NodeB.
The network may initiate a paging procedure when sending data (e.g., services or signaling) to UE. In this case, for example, the Mobile Management Entity (MME) may send a paging message (i.e., the paging request) to the eNodeB, and then the eNodeB searches for the related UE within its coverage area. This may occupy the radio resources of the eNodeB. The more paging messages the MME sends, the more resources are consumed.
Radio resources are limited and precious to save. In order to save the resources, conventionally, the paging area for UE will be expanded gradually as follows in the Packet Switch (PS) paging:                Last accessed eNodeB by UE. This is the minimum area to page the UE, a single eNodeB.        Last accessed Tracking Area (TA) by UE. All eNodeBs belonging to the same TA the UE last accessed would receive the paging request for the UE.        All TAs in the TA list assigned to the UE. All eNodeBs belonging to the TAs in the TA list would receive the paging request for the UE. The TAs include the ones which are adjacent to the last accessed TA, and the nonadjacent ones which are assigned to that UE in Attach/TAU (Tracking Area Update) Accept messages. Conventionally, in the LTE system, paging and location update are both based on the TA list.        
On one hand, in above expansion logic, the paging area is still big. For example, the paging request is sent to many eNodeBs within one TA, but only one eNodeB therein will answer it, then the hit rate is low when the area is expanded. However, if the area is narrowed, this may result in no answer from the eNodeB because the UE may move to another area, not in the area being paged. Here is the typical live configuration in the customer network, e.g., 30 eNodeBs would usually be configured per TA in average and even up to 50 eNodeBs for a TA from the customer site. In this case, the paging efficiency is low once the UE is paged in the last accessed TA, i.e. the hit rate will be 1/30˜1/50, even worse if expanding the paging area to the TAs in the TA list allocated to the UE.
On the other hand, in above expansion logic, the TAs in the TA list allocated to the UE may not be geographical neighbors. This result in the paging request sent to some areas can not be responded. Therefore, it is necessary to provide a more efficient paging method to save the radio resources.